Jane Blundell’s Ultimate Mixing Palette includes the highly granulating ochre Goethite Brown Oxide (PY43), with Monte Amiata Natural Sienna (PBr7) listed as an alternative. But what’s the difference between these two colors?

Goethite is browner and more granulating, and MANS is much yellower. While still granulating, it’s not as wildly so.
Color Mix Comparisons
Buff Titanium


The pastel-ization from the Buff Titanium emphasizes how very much yellower the MANS is. The Goethite is far more granulating and the granulation floats visibly in all levels of dilution, creating unparalleled sand mixes. MANS does not look to me to be nearly so appropriate for sand – it’s just far too yellow.
(With that said, I think the mix of MANS and Dioxazine Violet is good for sand. I also like Buff with a ‘Jane’s Grey’ type mix of Ultramarine and Burnt Sienna or Transparent Red Oxide. Lots of sand options!)
Transparent Red Oxide


Mixes with MANS are oranger and more vivid. Goethite mixes are more muted and potentially more appropriate for mid to light skin tones.
Quin Rose


More orangey, less granulating mixes with MANS.
Potter’s Pink


Similar brown-pink mixes. MANS is oranger. Granulation is much stronger in the Goethite mix.
Cobalt Blue


MANS is lighter value and yellower, but neither of these mixes make green! They are gray/brown/blues.
Cobalt Turquoise


More mixable with MANS, creating a variety of greens from aloe to olive. Goethite creates very visible granulation that doesn’t really mix.
Phthalo Green


Both colors make muted yellow-greens with texture, but as usual the MANS mixes are yellower and the Goethite mixes are browner and more wildly textured.
Conclusion
MANS and Goethite have a similar palette role as a yellow-brown ochre color with granulation. MANS is much yellower and less muted, and so its mixes are warmer and more vivid. Goethite is more granulating and its mixes are muted and have more texture.
My personal choice is MANS because I like brighter mixes and because MANS can create pale sunrise yellows, which Goethite can’t do. If you’re a granulation fan and you find it more important to make textured and muted tones, e.g. sand and foliage mixes, you may prefer Goethite.